MIRACLES OF SCIENCE 



merely more light but better-focused light that the 

 astronomer is forever seeking. 



But suppose you combine size and quality; have 

 your lens ground by an Alvan Clark, or your mirror 

 fashioned by a Ritchie; substitute your metal mirror 

 with a glass one superbly polished and thinly silvered 

 on the front surface. Suppose, then, that you trans- 

 fer your observatory from the heavy atmosphere of 

 the sea-level to the thin, clear air of the mountain 

 tops. Then conditions are achieved that bespeak 

 notable results. 



Such are the conditions under which work is done 

 at Lick Observatory and at Mt. Wilson. As the case 

 stands at the moment, the five-foot reflector at Mt. 

 Wilson is effectively the most powerful instrument in 

 existence, although as just noted it is not the largest. 

 The hundred-inch mirror now in process of construc- 

 tion at Mt. Wilson will, it is hoped, surpass by yet 

 another stage all previous efforts in the all-essential 

 work of light-gathering. 



The simplest test of a telescope is the capacity of 

 the instrument to bring new galaxies of stars into the 

 field of vision. At the outset we must recall that even 

 our planetary neighbors Uranus and Neptune are 

 invisible to the naked eye. So are all the little plan- 

 ets about seven hundred are known that people 

 the space between Mars and Jupiter. The total num- 

 ber of stars within the range of unaided vision is only 

 about five thousand. They are arbitrarily classified 

 as representing six magnitudes of light. 



But the telescope reveals galaxy on galaxy of 

 otherwise invisible stars, the numbers increasing in 



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